Sheet metal is an infinitely useful commodity that has helped our civilisation achieve some impressive feats such as erecting tall structures or constructing impressive machines that have worked towards benefiting people in their day-to-day lives. But whilst sheet metal machinery is responsible for shaping and refining this commodity into useful applications – what about the sheet metal itself? What process is used to create it? How is sheet metal finished? Well, stick around to find out.
The four stages
Sheet metal is created in just five stages: melting, pouring, pickling, oxidisation and rust protection and rolling and annealing.
- Melting
As we know – sheet metal can be made from several different types of metal such as aluminium, stainless steel and copper – each with their own properties. There are also different types of thicknesses (known as gauges) that they can be forged into which each has its own preferred uses. The melting stage is fairly self-explanatory as it’s where the metal is melted down into liquid form.
- Pouring
Once in liquid form – the metal can be poured into rectangular moulds so that it can take its shape. Once it has filled the mould it can begin to cool and harden into a solid piece.
- Pickling
Pickling is a process whereby impurities or any surface stains/marks are removed. This is done via an acid bath. Essentially – it’s a cleaning phase for the newly formed sheet to ensure the final product is in tip-top physical quality.
- Oxidisation protection (oiled steel)
Some metals need a little more work to be future-proofed. In other words, they must be protected from rust and oxidisation that may occur in the near future. Whilst aluminium, for example, forms its own oxide layer upon exposure to our atmosphere – materials such as steel do not have this luxury. So, a thin layer of oil is introduced onto a newly formed steel sheet to protect it. This is what the term oiled steel refers to.
- Rolling and annealing
After the sheet is rust-proof and cleared of physical abrasions – it can be altered to suit different lengths and gauges. This is done with rollers that constantly roll over the sheet to thin and stretch it out. The more times a sheet is rolled – the harder it becomes. Sometimes, annealing (the process of heating metal and letting it slowly cool) is required to counteract this and to ensure the desired outcome is achieved. If annealing is required – then the pickling process is also repeated. This does not mean the metal is melted back into liquid form, however – just made hot enough to alter.
Finishing sheet metal
Sometimes sheet metal is finished with a special coating to make it applicable to certain applications where standard sheets just won’t do the trick. We’ve spoken about the galvanisation process – but what about some of the other finishing methods?
- Anodised coating is the process of hardening the oxide layer to improve overall durability. It is often done to aluminium sheet metal. It also makes it:
- Easier to colour the metal during the process;
- More adhesive for paint and primers; and
- Flake and peel resistant.
- Powder coating is mostly used to create sturdy, coloured metal by applying paint powder electrostatically and allowing it to cure under heat. Some advantages include:
- A diverse range of possible colours and effects;
- Thicker coats and longer-lasting colours in comparison to liquid finishing methods; and
- The fact that it releases almost no volatile organic compounds into the environment – making it a green finishing alternative.
- Tinning is a fairly simple coating process where tinplate is electrolytically applied to steel or copper sheet metal. This is to prepare it for being turned into items such as food cans. Tinning is:
- Cost-effective;
- Highly durable; and
- Able to produce both a matte grey/white finish or a shiny, metallic one.
Are you looking to purchase sheet metal machinery?
Now that you know the basics of how sheet metal is made and some of the finishing processes that are used – it’s time to look at some quality sheet metal machinery to get your workshop started or to update your existing one. ACRA Machinery is your port of call for all your sheet metal machinery requirements. We stock a variety of new and used sheet metal machines such as slitter folders and laser cutters as well as offer on-site maintenance and repair services.
Please give us a call on 03 9794 6675 or fill out the contact form on our website if you’d like to get in touch with us.